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RRAM characteristics using a new Cr/GdOx/TiN structure.

Jana D, Dutta M, Samanta S, Maikap S - Nanoscale Res Lett (2014)

Bottom Line: After measuring 50 RRAM devices randomly, the 8-μm devices exhibit superior resistive switching characteristics than those of the 0.4-μm devices owing to higher recombination rate of oxygen with remaining conducting filament in the GdOx film as well as larger interface area, even with a thinner GdOx film of 9 nm.The GdOx film thickness dependence RRAM characteristics have been discussed also.Memory device shows repeatable 100 switching cycles, good device-to-device uniformity with a switching yield of approximately 80%, long read endurance of >10(5) cycles, and good data retention of >3 × 10(4) s at a CC of 300 μA.

View Article: PubMed Central - PubMed

Affiliation: Thin Film Nano Technology Laboratory, Department of Electronic Engineering, Chang Gung University, 259 Wen-Hwa 1st Rd., Kwei-Shan, Tao-Yuan, 333, Taiwan, debanjan.jana@gmail.com.

ABSTRACT
Resistive random access memory (RRAM) characteristics using a new Cr/GdOx/TiN structure with different device sizes ranging from 0.4 × 0.4 to 8 × 8 μm(2) have been reported in this study. Polycrystalline GdOx film with a thickness of 17 nm and a small via-hole size of 0.4 μm are observed by a transmission electron microscope (TEM) image. All elements and GdOx film are confirmed by energy dispersive X-ray spectroscopy and X-ray photoelectron spectroscopy analyses. Repeatable resistive switching characteristics at a current compliance (CC) of 300 μA and low operating voltage of ±4 V are observed. The switching mechanism is based on the oxygen vacancy filament formation/rupture through GdOx grain boundaries under external bias. After measuring 50 RRAM devices randomly, the 8-μm devices exhibit superior resistive switching characteristics than those of the 0.4-μm devices owing to higher recombination rate of oxygen with remaining conducting filament in the GdOx film as well as larger interface area, even with a thinner GdOx film of 9 nm. The GdOx film thickness dependence RRAM characteristics have been discussed also. Memory device shows repeatable 100 switching cycles, good device-to-device uniformity with a switching yield of approximately 80%, long read endurance of >10(5) cycles, and good data retention of >3 × 10(4) s at a CC of 300 μA.

No MeSH data available.


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XPS characteristics. (a) Broad and (b) narrow scan spectra. The Gd-rich GdOx film is confirmed. The thickness of the GdOx film was 17 nm.
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Fig1: XPS characteristics. (a) Broad and (b) narrow scan spectra. The Gd-rich GdOx film is confirmed. The thickness of the GdOx film was 17 nm.

Mentions: The Cr/GdOx/TiN RRAM devices were fabricated as follows. First, the SiO2 layer with a thickness of 200 nm was deposited on an 8-in Si substrate. Then, TiN as a bottom electrode (BE) was deposited on an SiO2/Si substrate. The thickness of TiN BE was approximately 200 nm. In next step, an SiO2 layer with a thickness of 150 nm was deposited on TiN BE. Then, the via-holes with different sizes ranging from 0.4 × 0.4 to 8 × 8 μm2 and BE contacts were designed and etched. Photo-resist was coated and patterned for switching material and the top electrode (TE) contacts. Therefore, another lithography step was used to pattern the devices for lift-off. After that, a small piece of approximately 1 × 1 in2 was cut from the 8-in patterned wafer and deposited consecutive switching material and the top electrode. The Gd2O3 as a resistive switching material was deposited by an electron-beam evaporation method. Pure Gd2O3 shots were used during evaporation. The deposition rate of Gd2O3 was 0.2 Å/s, and the power was 400 W. After deposition, the Gd2O3 material was a Gd-rich Gd2O3 film which was confirmed by X-ray photo-electron spectroscopy (XPS) analysis [22]. Broad scan of XP spectra is shown in Figure 1a. The Gd (3d, 4 s, 4p, and 4d), O1s, and C1s peaks are also observed. XPS spectra of Gd 3d5/2 and Gd2O3 3d5/2 peaks were located at 1186.73 eV and 1,189 eV, respectively, which confirmed a Gd-rich Gd2O3 film, i.e., GdOx (Figure 1b). The area ratio in between Gd and Gd2O3 is 1:0.89. This suggests that the as-deposited Gd2O3 film is a Gd-rich GdOx film. Then, the Cr TE was deposited by rf sputtering process. Argon (Ar) gas flow rate was 10 sccm during deposition. The deposition power and chamber pressure were 100 W and 6 mTorr, respectively. Finally, a lift-off process was performed to get the final RRAM device. The thickness of the GdOx film was 17 nm. For comparison, the thickness of the GdOx film was also 9 nm. Microstructure of a Gd2O3 film in the RRAM devices was carried out by using TEM-JEOL 2100 F system (JEOL Ltd., Akishima-shi, Japan) with energy of 200 keV and resolution of 0.2 nm. Memory characteristics were performed by using HP 4156C precision parameter analyzer system (Agilent Technologies, Inc., Santa Clara, CA, USA). During electrical measurement of the memory devices, the BE was grounded and the sweeping bias was applied on the TE. All measurements were characterized inside the black box on an 8-in chuck.Figure 1


RRAM characteristics using a new Cr/GdOx/TiN structure.

Jana D, Dutta M, Samanta S, Maikap S - Nanoscale Res Lett (2014)

XPS characteristics. (a) Broad and (b) narrow scan spectra. The Gd-rich GdOx film is confirmed. The thickness of the GdOx film was 17 nm.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4493994&req=5

Fig1: XPS characteristics. (a) Broad and (b) narrow scan spectra. The Gd-rich GdOx film is confirmed. The thickness of the GdOx film was 17 nm.
Mentions: The Cr/GdOx/TiN RRAM devices were fabricated as follows. First, the SiO2 layer with a thickness of 200 nm was deposited on an 8-in Si substrate. Then, TiN as a bottom electrode (BE) was deposited on an SiO2/Si substrate. The thickness of TiN BE was approximately 200 nm. In next step, an SiO2 layer with a thickness of 150 nm was deposited on TiN BE. Then, the via-holes with different sizes ranging from 0.4 × 0.4 to 8 × 8 μm2 and BE contacts were designed and etched. Photo-resist was coated and patterned for switching material and the top electrode (TE) contacts. Therefore, another lithography step was used to pattern the devices for lift-off. After that, a small piece of approximately 1 × 1 in2 was cut from the 8-in patterned wafer and deposited consecutive switching material and the top electrode. The Gd2O3 as a resistive switching material was deposited by an electron-beam evaporation method. Pure Gd2O3 shots were used during evaporation. The deposition rate of Gd2O3 was 0.2 Å/s, and the power was 400 W. After deposition, the Gd2O3 material was a Gd-rich Gd2O3 film which was confirmed by X-ray photo-electron spectroscopy (XPS) analysis [22]. Broad scan of XP spectra is shown in Figure 1a. The Gd (3d, 4 s, 4p, and 4d), O1s, and C1s peaks are also observed. XPS spectra of Gd 3d5/2 and Gd2O3 3d5/2 peaks were located at 1186.73 eV and 1,189 eV, respectively, which confirmed a Gd-rich Gd2O3 film, i.e., GdOx (Figure 1b). The area ratio in between Gd and Gd2O3 is 1:0.89. This suggests that the as-deposited Gd2O3 film is a Gd-rich GdOx film. Then, the Cr TE was deposited by rf sputtering process. Argon (Ar) gas flow rate was 10 sccm during deposition. The deposition power and chamber pressure were 100 W and 6 mTorr, respectively. Finally, a lift-off process was performed to get the final RRAM device. The thickness of the GdOx film was 17 nm. For comparison, the thickness of the GdOx film was also 9 nm. Microstructure of a Gd2O3 film in the RRAM devices was carried out by using TEM-JEOL 2100 F system (JEOL Ltd., Akishima-shi, Japan) with energy of 200 keV and resolution of 0.2 nm. Memory characteristics were performed by using HP 4156C precision parameter analyzer system (Agilent Technologies, Inc., Santa Clara, CA, USA). During electrical measurement of the memory devices, the BE was grounded and the sweeping bias was applied on the TE. All measurements were characterized inside the black box on an 8-in chuck.Figure 1

Bottom Line: After measuring 50 RRAM devices randomly, the 8-μm devices exhibit superior resistive switching characteristics than those of the 0.4-μm devices owing to higher recombination rate of oxygen with remaining conducting filament in the GdOx film as well as larger interface area, even with a thinner GdOx film of 9 nm.The GdOx film thickness dependence RRAM characteristics have been discussed also.Memory device shows repeatable 100 switching cycles, good device-to-device uniformity with a switching yield of approximately 80%, long read endurance of >10(5) cycles, and good data retention of >3 × 10(4) s at a CC of 300 μA.

View Article: PubMed Central - PubMed

Affiliation: Thin Film Nano Technology Laboratory, Department of Electronic Engineering, Chang Gung University, 259 Wen-Hwa 1st Rd., Kwei-Shan, Tao-Yuan, 333, Taiwan, debanjan.jana@gmail.com.

ABSTRACT
Resistive random access memory (RRAM) characteristics using a new Cr/GdOx/TiN structure with different device sizes ranging from 0.4 × 0.4 to 8 × 8 μm(2) have been reported in this study. Polycrystalline GdOx film with a thickness of 17 nm and a small via-hole size of 0.4 μm are observed by a transmission electron microscope (TEM) image. All elements and GdOx film are confirmed by energy dispersive X-ray spectroscopy and X-ray photoelectron spectroscopy analyses. Repeatable resistive switching characteristics at a current compliance (CC) of 300 μA and low operating voltage of ±4 V are observed. The switching mechanism is based on the oxygen vacancy filament formation/rupture through GdOx grain boundaries under external bias. After measuring 50 RRAM devices randomly, the 8-μm devices exhibit superior resistive switching characteristics than those of the 0.4-μm devices owing to higher recombination rate of oxygen with remaining conducting filament in the GdOx film as well as larger interface area, even with a thinner GdOx film of 9 nm. The GdOx film thickness dependence RRAM characteristics have been discussed also. Memory device shows repeatable 100 switching cycles, good device-to-device uniformity with a switching yield of approximately 80%, long read endurance of >10(5) cycles, and good data retention of >3 × 10(4) s at a CC of 300 μA.

No MeSH data available.


Related in: MedlinePlus